<!DOCTYPE html>
<html>
<head>
<title>Rounded rectangle clipping test</title>
<style>
.clipround {
  left:100px;
  top:100px;
  position:absolute;
  width:700px;
  height:380px;
  overflow:hidden;
  border-radius:45px;
}
canvas {
  position:absolute;
}
#nrcCanvas0 {
  left:0px;
  top:0px;
}
#nrcCanvas1 {
  left:320px;
  top:0px;
}
#nrcCanvas2 {
  left:0px;
  top:240px;
}
</style>
</head>

<body>
<div class="clipround">
<canvas id="nrcCanvas0" width="320" height="260"></canvas> 
<canvas id="nrcCanvas1" width="320" height="260"></canvas>
<canvas id="nrcCanvas2" width="320" height="260"></canvas> 
</div>

<script>
  drawShapes('nrcCanvas0');
  drawShapes('nrcCanvas1');
  drawShapes('nrcCanvas2');
    
  function drawShapes(elName) {
    var ctxt = document.getElementById(elName).getContext('2d');
    ctxt.fillStyle = '#00ff00';
    ctxt.fillRect(0, 0, 300, 230);
  }
</script>
</body>
</html>
